1. Field of the Invention
The present invention relates to an apparatus and methods for separating plasma from blood and, more specifically, to an apparatus and methods where plasma can be removed from blood without other unwanted blood components including, for example, lipids and lipoproteins which are present in the blood.
2. Description of the Related Art
WO 96/16714 discloses a container for separating a blood or plasma component, e.g., fibrin monomer, from blood or plasma by a centrifugation about a vertical axis. The container comprises a first annular chamber defined by an outer cylindrical wall and an inner cylindrical wall, both walls extending coaxially about a common axis, as well as by a top wall and a bottom wall, where the bottom wall is formed by a piston displace able within the first chamber. The container further comprises a second chamber accommodated below the first chamber and communicating with the first chamber through a first conduit. The second chamber is defined by the outer cylindrical wall, the bottom wall of the first chamber, and by a second bottom wall. This second chamber serves as reaction chamber for receiving plasma and treating the plasma to obtain the desired component.
Placing this container in a centrifuge for the above-described reaction provides that the non-crosslinked fibrin polymer is separated from the plasma and deposited on an outer wall of the reaction chamber during centrifugation. When the piston is subsequently actuated, the remaining plasma is removed from the reaction chamber. Thereafter, a solvent is added for dissolving the so-deposited, non-crosslinked fibrin polymer and forming the desired fibrin monomer solution.
As described in detail in EP 592242 this fibrin monomer solution is extremely useful, for example, in fibrin sealant methods, and it is desirable to use devices like those described in U.S. Pat. No. 5,603,845, WO 96/16713, WO 96/16714 and WO 96/16715 to prepare blood products, such as fibrin sealant components, immediately at the time of surgery so that autologous blood can be utilized.
A disadvantage of some known devices for separating plasma from blood is that when the plasma is removed unwanted components of the blood that are less dense than the plasma, are sometimes also removed with the plasma in undesirable amounts.
Accordingly, it is an object of the invention is to provide an apparatus and methods for improved separation of plasma from blood, without also removing unwanted components, such as lipids and lipoproteins, from the blood.
This objective and other objectives are achieved by providing an apparatus for separating plasma from blood, the apparatus including a first chamber for centrifuging the blood to obtain the plasma. The first chamber includes an inner wall, an outer wall, a top wall and a bottom wall, the bottom wall being movable in the first chamber from a first position for receiving and centrifuging the blood to a second position for expelling from the first chamber plasma separated from the blood. A retaining means is located in the first chamber for retaining blood components less dense than the plasma in the first chamber when the plasma is being expelled by movement of the bottom wall from the first position to the second position in the first chamber. A second chamber is provided which is in fluid communication with the first chamber, the second chamber receiving the plasma expelled from the first chamber when the bottom wall is moved from the first position.
There is also provided an improved method for separating plasma from blood. Blood is centrifuged in a first chamber to obtain a plasma portion of the blood and additional blood components having a density less than the density of the plasma portion. The plasma portion is then removed from the first chamber while simultaneously retaining in the first chamber the less dense components of the blood.